It has long been considered desirable to allow telephone subscribers as much control as possible in the processing of calls, thereby reducing the need for operators and enhancing the privacy of telephone communication. Such subscriber controlled services have primarily been directed to calling parties in the past. Direct Distance Dialing (DDD) is a prime example of such a type of service in the telephone network. A more recent example is Automatic Bill Calling (ABC) service, described in Mearns U.S. Pat. No. 4,162,377 of July 24, 1979. In ABC calling, calling parties may control the completion of special calls such as credit card, collect, and bill to third number, all without operator intervention.
It is also desirable for called parties to be able to control the disposition of calls directed to them. For example, it is desirable for a called party to be able to control the diversion of calls to telephone stations other than the station at which the called party normally resides. In fact, such a service, usually referred to as call-forwarding, is currently available to many subscribers who are served by stored program electronic switching offices, such as the ESS (Electronic Switching System) No. 1, manufactured by Western Electric Co., Inc. A party served by a local ESS 1 office and who subscribes to call-forwarding service has stored in memory at the office data identifying the party as a subscriber. In addition, data is also stored at the office indicating if the service is activated and, if so, a directory number to which incoming calls are to be forwarded. Briefly, the service operates as follows. When an incoming call is received, the stored program of the office directs the interrogation of the memory data associated with the called station to determine if the called party subscribes to call-forwarding service. If not, or if the service is not activated, the call is completed to the called station in ordinary fashion. If a call-forwarding service, however, is active for the party, the stored program obtains the forwarding number from memory and from that point acts, effectively, as an originating office with respect to the new number. That is, the office may complete the call locally to the new number if it is served by the office, or it may seize an outgoing trunk to another local office or to the toll network, as the situation demands, and outpulse the new number to a distant office to complete the call.
U.S. Pat. No. 3,555,196, which issued to F. J. Singer on Jan. 12, 1971, discloses a programmed auxiliary control arrangement for upgrading crossbar type telephone offices with call-forwarding capability. Such a crossbar type office is disclosed in U.S. Pat. No. 2,585,904, which issued to A. J. Busch on Feb. 19, 1952. A crossbar office modified by the arrangement is described in the patent as completing functions similar to those described above for the ESS 1.
For parties not served by local offices with call-forwarding ability, call-diverting circuits are commercially available. These circuits attach to a station at a party's premises; in response to a completing call, such a circuit initiates a new outgoing call on a different line to a preselected number and eventually interconnects the two calls at the called party's premises.
In general, the arrangements described above have the ability to forward a call, under called party control, to any other compatible telephone station regardless of location. The telephone service offered, however, is limited. There are a host of other services that would be desirable to place under called party control to offer a more complete call completion service. For example, it is desirable to allow subscribers to control the denial of calls for any number of reasons. It may also be desirable to give the caller an indication of why a call is denied. This might be valuable in business relationships, for example, where a caller needs to have some expectation of when his party might be reached. In addition, a caller may wish to record the fact of the call and the identity of the caller so that the called party may return the call at the earliest possible moment. Called party controlled services of the past and present, such as call forwarding, do not offer such flexibility.
Call forwarding service has a number of other disadvantages. For example, subscribers today can activate, deactivate, and update forwarding numbers in their call-forwarding service only from their primary station. Thus, a subscriber normally residing in New York, but temporarily in California, cannot modify his call-forwarding service without enlisting the aid of another person having access to, say, his home phone. Not only is this inconvenient, but undesirable in terms of revealing information that the subscriber may wish to keep private.
Another practical difficulty inherent in conventional call-forwarding systems is that, in effect, two completely independent telephone connections are required to forward a call. The first connection is from the calling station to the local office serving the called party. The second connection is from that local office to the local office serving the forwarded number. In general, the quality of the overall connection is detrimentally affected by the average increased length of the connection. The factors contributing to this include transmission loss, increased signal distortion, increased echo, increased call setup time and the like. Moreover, the number of facilities, such as trunks and office supervisory and switching circuits, required to complete a forwarded call are undesirably increased. In an extreme case, for example, a call may be routed from the West Coast to the East Coast only to be forwarded to the West Coast again for completion. Add to this the alternate routing that may automatically occur in the telephone network during periods of dense traffic, disaster, and the like, and the potential practical difficulties of call-forwarding become evident.